I don't have the value. There appears to be two different versions. In the photos that I have, there is only one 3.9k resistor and an open space (no pads) where the resistor is missing in your board.

When you install it, I'd suggest leaving about 1/4" of clearance between it and the board. The board has been damaged by the heat and installing it off of the board will prevent it from transferring so much heat to the board (due to longer lead length and more clearance between the body of the resistor and the board).

Perry is correct there are two versions of this board. I do not have any factory info about this early board, sorry.

PG had two version of the ZPA line. This appears to be a Version 1 ZPA amp. The problem you have pictured was a serious issue in the early production of the product line so they redesigned the board circuitry to fix this issue and to remove the ground float switch located near the RCA inputs. Version 1 had red wire on the toroids, this board issue, and a RCA float switch near the RCAs.

Version 2 had green wire on the toroids and no RCA float switch < it had been removed and hard wired > and this board was replaced completely with the new design to solve the excessive Voltage drop issues that caused the issues you have pictured.

You might want to try and contact PG/AAMP aka Stinger in Florida and see if they will sell you a replacement board. Or do as Perry suggests and raise the resistors away from the board as much as possible to limit the heat damage. I also suggest you use silver solder on the connections it has a slightly higher melting point, so it withstands higher heat loads better.

Ok you have a Version 2 amp, and the little resistors that are burnt in your last few pictures tell me you have a blown channel also. The resistors are current limits for each stage so the amp does not damage the board severely when it fails like it has.

I own several of these so I can reference mine to give you any parts ID you might need. I just need to pull one out of storage. For now though it looks like a rebuild of at least one channel.
The channels are mirror images of each other in most cases, but I will gladly assist you in any way to verify any parts values you might be in doubt about. If you like you can PM me and we can do this thru direct email in order to avoid a very lengthy public thread.
Either way I will try to help you as needed. So let me know what parts ID you might need, and IMHO be ready to replace a lot of parts on the channel with the burnt resistors.